Hello Volker,
From SAPUI5 Runtime Libraries Server Version Check,
When you develop SAPUI5 applications with SAPUI5 application development tools, the code completion and application preview features are based on SAPUI5 runtime libraries installed in your Eclipse. However, after you have deployed the application to the ABAP server and execute it there, it will use the SAPUI5 runtime libraries installed on the ABAP server.
As for how to prevent the warning message,
When testing in Eclipse you should configure it to use the runtime libraries located on the server instead of the local ones, see SAPUI5 Library Location Used for Testing.
Hope this helps,
Scott